Prevalence of the microbiological causes of canine otitis externa and the antibiotic susceptibility of the isolated bacterial strains

Otitis externa is a canine disease of multifactorial etiology in which bacteria plays a significant role. Due to the predominant bacterial etiology otitis is usually treated with antibiotics. However, non-prudent use of antibiotics promotes the emergence of antibiotic-resistant bacteria thus compromising the therapy effectiveness. Currently, the increase of antimicrobial resistance (AMR) is one of the biggest threats to global health. For this reason, the aim of the study was to investigate prevalence of the microbiological causes of canine otitis externa and the antibiotic susceptibility of the isolated bacterial strains. The research and sampling were conducted at Veterinary Clinics for small pets in Serbia. Samples were sent to laboratory for bacteriological and mycological testing. Additionally, the sensitivity of the isolated bacteria to antibiotics was evaluated using disc diffusion method. Sixty dogs with otitis externa clinical symptoms were included in the study. Out of a total of 53 positive samples for pathogen presence, bacteria were present in 40. The most prevalent bacteria was Staphylococcus pseudintermedius, followed by Pseudomonas aeruginosa and Proteus spp., while Malassezia pachydermatis was the only isolated yeast pathogen occurring in 36 samples. Generally, the lowest resistance against all bacteria showed enrofloxacin. On the contrary, high resistance to penicillin and amoxicillin was a common finding for G+ and G- bacteria. These results indicate the need for laboratory testing in terms of isolation, identification and antibiotic susceptibility testing, not only in the case of otitis externa in dogs, but in all diseases when it is possible, in order to enhance antimicrobial stewardship and consequently to contribute AMR reduction.